1. Field of the Invention
The present invention relates to an apparatus for controlling the exposure of an electronic camera mounted on electronic equipment such as portable information terminal devices.
2. Description of the Related Art
Some electronic devices called portable information terminal devices, such as notebook personal computers and PDAs (personal digital assistants), are equipped with a video camera for capturing images of an operator of the electronic device or images of other objects and for displaying the images on a display screen of the electronic device. In such electronic devices, typically, an imager of the video camera is attached to an upper portion of a display so that the camera can be rotated in a plane orthogonal to the screen. The imager may be rotated as desired in order to photograph the operator of the electronic device or an object located on the opposite side of the electronic device. The electronic devices further include an exposure controller for the video camera for detecting the brightness of a captured image to automatically control the video camera to an appropriate exposure level.
Generally, outdoor photography often produces a backlighting problem because the sky is included in an upper portion of a photographic image, while indoor photography often produces an excessive front lighting problem because a ceiling light is included in an upper portion of a photographic image. A typical approach to photograph an object in a manner as real as possible during such conditions is to divide a single photographic image into an upper area and a lower area for exposure control so that the brightness detected in the lower area is more strongly reflected.
If the operator of the electronic device captures an image of himself/herself indoors with the imager of the video camera pointing towards the operator, however, a window or a light may often be behind the operator at an upper portion or a side portion in the image, thus causing a backlighting or excessive front lighting problem. In this case, the above-noted approach to detect the brightness in the upper and lower areas into which a photographic image is divided does not provide accurate exposure control, resulting in dim photography of the operator to produce an obscure image.